Tangential and normal conductivities of Nafion® membranes used in polymer electrolyte fuel cells

Investigations of conductivity in FEP-based radiation-grafted alkaline anion-exchange membranes

“…In contrast, Pozio et al took the membrane thickness to be the nominal value of 127 µm and only soaked the N115 MEAs in water after hot pressing ( = 10), which, as stated by these authors, would not fully hydrate the N115 membrane to the expanded E-form with a restored hydrophilic cluster structure. However, the values of conductivities obtained in this study for N115 correlate well with values for fully hydrated ( = 22 -23) Nafion ® membranes obtained from previous studies using different normal and tangential methods as reviewed in Tables 1 and 2 in Reference [28].…”

“…As the sample standard deviation over the three samples is the same magnitude as the CIEs, there is no significant variability between the MEAs of each sample of N115 when measuring the conductivities using this method and cell setup. The conductivity values obtained are much larger that those obtained by Pozio et al for N115 ( = 0.045 ± 0.004 S cm -1 at 65°C) [28]. This can be explained by the fact that in this study the N115 MEAs were boiled for 2 h in water to reproduce the fully hydrated expanded form after hot-pressing and that the membrane thickness was taken as 140 ± 9 µm.…”

“…After pressing, the resulting membrane electrode assemblies (MEAs) were stored in water for at least two days prior to conductivity measurements. The cell design, with circular graphite plates, was similar to that reported by Pozio [28], the only difference being that ELAT A-6 carbon cloth electrodes were used instead of Toray carbon paper. The cell assembly was placed in a beaker of RO water so that all of the MEA was submerged, while the gold jack plug Commercial Nafion ® -115 (N115) proton-exchange membrane (fully hydrated thickness determined to be 140 ± 9 µm) was used as a benchmark.…”

“…The method for measuring the conductivities followed the impedance spectroscopy approach recently reported by Pozio et al [28,29]. Impedance spectra were recorded with a Solartron 1260 frequency response analyser / 1287 electrochemical interface combination controlled by ZPlot v.1 software (Scribner Associates) with data analysis of the Nyquist plots (Z im vs Z real from the vector (in the complex plane), Z( ) = R + j , where the resistance R = Z real , the reactance = Z im , = 2 f (f is the frequency of the applied a.c. voltage), and j = 1 ) was conducted using Zview v.2 software (Scribner Associates).…”

“…the MEAs were pressed at 135°C for 5 min instead of 100°C and the MEAs were boiled in water for 2 h after preparation to ensure the expanded form of N115 was reformed after the hot pressing [28] (no delamination of the MEAs was observed in this boiling step). The N115 MEAs were then stored in water until required for impedance spectroscopy.…”